How to minimise and slow water flow rates thus reducing flooding

“How to minimise and slow water flow rates thus reducing flooding by use of ecological planting and sustainable urban design techniques in the landscape.”

As Britain braces itself for more wet weather in December, the high rain fall levels last week which led to flooding in Cumbria lead us to ask again; how can we minimise and slow water flow rates thus reducing flooding by use of ecological planting and sustainable urban design techniques in the landscape?

The high rainfall which caused the flooding last week in Cockermouth, Cumbria, was so extreme that the Environment Agency said that a flooding event was likely to happen only once in 1,000 years. However with the El Nino effect, this once in a 1,000 year rainfall event may become increasingly common in Britain and elsewhere, in wet months, when high rainfall continues to fall on already saturated ground. We really do need to press on with the implementation of recommendations as set out by The Pitt report.

Floods are notoriously difficult to predict, for meteorological and earth science reasons. Sheer scale of human tragedy and loss, plus millions of pounds worth of damage, mean that modelling firms must continue to work apace to search for ways of accurately predicting floods.

However, we must also seek swift and widespread landscape design and ecologically sound landscape management solutions to flood alleviation.
1) We will need to start planting more trees, in river catchment areas, such as the Cumbrian hills. We all need to contemplate planting more trees where space allows, as this will help to slow rainwater flow rates, giving more time to react to flooding- saving lives.
2) Woodlands should be actively managed and schemes integrated into flood management.
3) Deciduous trees are best as their leaf litter helps to absorb the rainfall and this helps to slow surface water flow rates following high rainfall, thus lowering the incidence of flooding.
4) We need to increase water storage on upland areas, rather than drain these areas too quickly as has been done in the past (where drains placed in Victorian times still hasten the flow of water from upland areas for historically traditional land management practices such as grazing by sheep.)
5) Designing large lakes and ponds and SUDs for upland areas and river catchments with high rainfall and other areas with a propensity towards flooding would help.
6) Designing flood alleviation schemes in flood risk areas should continue.
7) All new parking areas and housing hard surfacing must be designed to be permeable, so that water flow rates are slowed, minimising flooding in neighbouring areas downstream.
8) Convert impermeable hard surfacing into permeable surfacing.

Rainfall on this occasion was unusually high;“the highest level measured in England since records began.” (The Times, Nov 21st, 2009) “Meteorologists recorded 314mm (12in) of rain in 24 hours”; the rainfall was also widespread;“ flood warnings remained in place across North West of England, parts of Wales, Scotland and Northern Ireland;” (The Times, 21st Nov 2009

Professional, pragmatic and innovative skills and research continue to be required to help to produce practical solutions to minimise and slow water flow rates thus reducing flooding. Planting and sustainable urban design techniques can help to minimise flooding due to high rainfall events. For more information visit our flooding web page http://www.landvision.co.uk/services_flooding.html